Ultra short high pressure gradient flow path flow field

ABSTRACT

The present invention is directed to a planar flow field design having an intake manifold and an exhaust manifold which are configured in two offset planes. A relatively short passage extends from the intake manifold through the exhaust manifold and terminates at a reactive face of a membrane electrode assembly (MEA) such that a differential flow distribution is provided from the intake manifold through the passage and across a reactive face of the MEA to the exhaust manifold.

FIELD OF THE INVENTION

The present invention relates to PEM fuel cells and more particularly toa separator flow field plate in which relatively small pressure drop isrequired to achieve the necessary flow rates.

BACKGROUND OF THE INVENTION

Fuel cells have been used as a power source in many applications. Forexample, fuel cells have been proposed for use in electrical vehicularpower plants to replace internal combustion engines. In proton exchangemembrane (PEM) type fuel cells, hydrogen is supplied as the fuel to theanode of the fuel cell and oxygen is supplied as the oxidant to thecathode. PEM fuel cells include a membrane electrode assembly (MEA)comprising a thin, proton transmissive, non-electrically conductive,solid polymer electrolyte membrane having the anode catalyst on one faceand the cathode catalyst on the opposite face. The MEA is sandwichedbetween a pair of non-porous, electrically conductive elements or plateswhich (1) serve as current collectors for the anode and cathode, and (2)contain appropriate channels and/or openings formed therein fordistributing the fuel cell's gaseous reactants over the surfaces of therespective anode and cathode catalysts.

The term “fuel cell” is typically used to refer to either a single cellor a plurality of cells (stack) depending on the context. A plurality ofindividual cells are typically bundled together to form a fuel cellstack and are commonly arranged in electrical series. Each cell withinthe stack includes the membrane electrode assembly (MEA) describedearlier, and each such MEA provides its increment of voltage. A group ofadjacent cells within the stack is referred to as a cluster.

In PEM fuel cells, hydrogen (H₂) is the anode reactant (i.e., fuel) andoxygen is the cathode reactant (i.e., oxidant). The oxygen can be eithera pure form (O₂) or air (a mixture of O₂ and N₂). The solid polymerelectrolytes are typically made from ion exchange resins such asperfluoronated sulfonic acid. The anode/cathode typically comprisesfinely divided catalytic particles, which are often supported on carbonparticles, and mixed with a proton conductive resin. The catalyticparticles are typically costly precious metal particles. As such theseMEAs are relatively expensive to manufacture and require certainconditions, including proper water management and humidification andcontrol of catalyst fouling constituents such as carbon monoxide (CO),for effective operation.

Traditionally, the electrically conductive plates sandwiching the MEAscontain a reactant flow field for distributing the fuel cell's gaseousreactants (i.e., hydrogen and oxygen in the form of air) over thesurfaces of the respective anode and cathode (referred collectivelyherein as active area). These reactant flow fields conventionallyinclude a plurality of lands that define a plurality of flow channelstherebetween through which the gaseous reactants flow from a supplyheader at one end of the flow channels to an exhaust header at theopposite end of the flow channels.

The requirements for a well-performing flow field may be characterizedinto local requirements and global requirements. A local requirementgenerally applies to every point on the active area and a globalrequirement applies to the entire flow field design. To satisfy thelocal requirements of a well-performing flow field, the flow fieldshould (1) deliver gas and humidification, (2) remove exhaust gases and(3) remove liquid water. To satisfy the global requirements of awell-performing flow field, the flow field should (4) satisfy localrequirements at all points on the active area, (5) satisfy localrequirements with a reasonably low overall pressure drop, (6) satisfylocal requirements consistently over time thus producing stable flow,and (7) satisfy local requirements at all required flow and loadconditions.

The requirement for stable flow (6), is a difficult requirement to meet.Two reasons may be cited for this difficulty. First, it is difficult todetermine exactly when stable flow has been achieved because there ismore than one condition under which it can be successfully accomplished.Stable flow requires the consistent removal of liquid water. However,water can be removed in more than one way. For example, in some casesgas velocity may be sufficiently high such that collection of liquidwater is not possible. In other cases, liquid water may collect and thena pressure build up may occur, causing the liquid water to move out. Insome cases low gas velocity and an inability to build pressure causeunfavorable water removal conditions and an unstable gas flow.

The second reason stable flow is difficult to meet is that in order tosatisfy it, other flow field requirements must be compromised. Forexample, the aspects of a flow field design that satisfy requirements(3) and (6) directly compete with design aspects that satisfyrequirements (4) and (5).

The following three examples demonstrate the difficulty in designing aflow field that can satisfy all requirements concurrently, includingestablishing either one of the two possible stable flow conditionsneeded for consistent water removal. In a first example, it is possibleto achieve stable flow by establishing a high gas velocity condition. Ahigh gas velocity condition is established by designing a flow pathhaving a high pressure gradient. However, for an averaged-sized activearea, the consequence of such a design is a flow field having anunacceptably high overall pressure drop. In this way, requirements (3),(4), and (6) are met while (5) is not satisfied.

In a second example, in order to reduce the overall pressure drop,Example 1 may be modified to have more parallel flow paths that areshorter in length. However, in reaching an acceptably low pressure drop,gas velocities become reduced to a level where liquid water is allowedto build up. Then, with the establishment of many parallel flow paths,removal of liquid water by a pressure build-up is no longer possiblebecause a pressure build-up cannot be raised. Accordingly, requirements(4) and (5) are met while (3) and (6) remains unsatisfied.

In a third example, in order to facilitate liquid removal by a pressurebuild-up, Example 2 may be modified by taking away some of the parallelflow paths. However, if the requirement of a low overall pressure dropis to be maintained, the length that can be added to each flow path tocompensate for removing flow paths is limited. In this case, all therequirements are met except the one requiring the flow field to coverthe entire active area. Specifically, requirements (3), (5) and (6) aremet and (4) is not satisfied.

SUMMARY OF THE INVENTION

The present invention is directed to a flow field design for achievingstable gas flows in the presence of liquid water, as well as forheightening the oxygen partial pressure in the catalyst layer in orderto raise cell performance. The flow field design includes an intakemanifold and an exhaust manifold which are configured in two offsetplanes. A relatively short passage extends from the intake manifold tothe exhaust manifold and terminates at a diffusion medium such thatfluid communication is provided from the intake manifold through thepassage and the diffusion medium to the exhaust manifold. Thus, thepresent invention may be employed to establish convective,interdigitated-like flow through a diffusion medium in order to raisethe oxygen partial pressure at the catalyst layer.

In one aspect, the present invention is directed to a fuel cell havingan first manifold defined between an membrane electrode assembly (MEA)and a first gas-impermeable element with a set of spacers disposed inthe first manifold. A second manifold is defined between the firstplanar element and a second gas-impermeable element. The firstgas-impermeable element and the spacers have an orifice formedtherethrough such that a flow path is established from the firstmanifold across a reactive face of the MEA to the second manifold.

In another aspect, the present invention is directed to a fuel cellhaving an MEA, a first separator sheet disposed in spaced relation tothe diffusion medium sheet to define a first manifold therebetween and afirst set of spacers disposed in the first manifold, each of the firstset of spacers having an orifice transverse to the first manifold formedtherein. A second separator sheet is disposed in spaced relation to thefirst separator sheet to define a second manifold therebetweentransverse to the orifice, and a second set of spacers are disposed inthe second manifold. A flow path is defined between the first manifoldand the second manifold through the orifice across the reactive face ofthe MEA.

In yet another aspect, the present invention is directed to a method ofmaking a separator plate for a fuel cell in which a first conductivesheet is laminated onto a first film sheet, and a portion of said firstconductive sheet is removed from the first film sheet such that aremaining portion of the first conductive sheet defines a first array ofspacers. A passage is formed through each of the spacers in the firstarray of spacers and the first film sheet to establish a series ofparallel flow paths. A second conductive sheet is laminated onto asecond film sheet, and a portion of the second conductive sheet isremoved from the second film sheet such that a remaining portion of thesecond conductive sheet defines a second array of spacers. The secondarray of spacers are laminated to the first film sheet opposite thefirst array of spacers such that a first manifold is formed between thefirst film sheet and the second film sheet.

Further areas of applicability of the present invention will becomeapparent from the detailed description provided hereinafter. It shouldbe understood that the detailed description and specific examples, whileindicating the preferred embodiment of the invention, are intended forpurposes of illustration only and are not intended to limit the scope ofthe invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thedetailed description and the accompanying drawings, wherein:

FIG. 1 is an isometric exploded view of a fuel cell including a pair ofcomplimentary spring seals in a PEM fuel cell stack;

FIG. 2 is a partial exploded perspective view of the bipolar plateillustrated in FIG. 1;

FIG. 3A is a plan view of the exhaust side of a separator plateaccording to a preferred embodiment of the present invention;

FIG. 3B is a plan view of the inlet side of the separator plate of FIG.3A;

FIG. 4A is a partial cross-sectional view of the separator plate of FIG.3A taken along line 4-4;

FIG. 4B is a partial cross-sectional view of the separator plate of FIG.4A illustrating the respective delivery, active area and exhaust legs ofthe flow path;

FIG. 4C is a detail of the inlet side of the separator plate;

FIG. 4D is a detail of the exhaust side of the separator plate;

FIG. 5A is a partial plan view of the inlet side of a separator plateaccording to an alternate embodiment of the present invention;

FIG. 5B is a partial plan view of the inlet side of a separator plateaccording to another alternate embodiment of the present invention;

FIG. 6A is a cross-sectional view of a bipolar plate taken through theinlet header;

FIG. 6B is a cross-sectional view of a bipolar plate taken through theexhaust header; and

FIG. 7 is a flow diagram illustrating steps for making a separator plateaccording to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The following description of the preferred embodiment is merelyexemplary in nature and is in no way intended to limit the invention,its application, or uses.

FIG. 1 schematically depicts a partial PEM fuel cell stack 10 havingmembrane-electrode-assemblies (MEAs) 14, 16 separated from each other bya non-porous, electrically-conductive bipolar plate 20. The MEAs 14 and16 and bipolar plate 20 are stacked together between non-porous,electrically-conductive, bipolar plates 22 and 24. Flow-interferingmedia 26, 28, 30 and 32 which are porous, gas-permeable, andelectrically conductive sheets press up against the electrode faces ofthe MEAs 14 and 16 and serve as primary current collectors for theelectrodes. The flow-interfering media 26, 28, 30 and 32 also providemechanical supports for the MEAs 14 and 16, especially at locationswhere the MEAs are otherwise unsupported in the flow field. Theflow-interfering media 26, 28, 30 and 32 further provide a fluidtransport mechanism from the inlet manifold across the reactive face ofthe MEA to the exhaust manifold.

Bipolar plates 22 and 24 press up against the primary current collector26 on the reactive cathode face 14c of the MEA 14 and the primarycurrent collector 32 on the reactive anode face 16 a of the MEA 16. Thebipolar plate 20 presses up against the diffusion medium 28 on thereactive anode face 14 a of the MEA 14 and against the primary currentcollector or diffusion medium 30 on the reactive cathode face 16 c ofthe MEA 16. An oxidant gas such as oxygen or air is supplied to thecathode side of the fuel cell stack 10 from an oxygen or air source 38via appropriate supply plumbing 40. Similarly, a fuel such as hydrogenis supplied to the anode side of the fuel cell stack 10 from a hydrogensource 48 via appropriate plumbing 50.

With reference now to FIGS. 2, 3A, 3B and 4A a separator plate 60according to the present invention will be described in greater detail.The separator plate 60 is configured to carry one of the reactant gasesto a respective face of the MEA 16. It is appreciated that each bipolarplate 20, 22 and 24 comprise two separator plates 60 lying in a back toback orientation (FIGS. 5A and 5B). Separator plate 60 includes a firstarray of electrically conductive spacers or disks 64 arranged along agas-impermeable sheet 66. An orifice 72 is formed through spacer 64 andsheet 66. Separator plate 60 also includes a second array ofelectrically conductive spacers or pillars 68 arranged along agas-impermeable sheet 76. As best seen in FIGS. 6A and 6B, an inletheader 80A, 80C communicates reactant gas from the appropriate supplyplumbing 40, 50 into the separator plate 60. An exhaust header 82A, 82Cremoves exhausted gas from the separator plate 60 as will be described.

As presently preferred, the spacers 64 in the first array are circulardisks having a diameter of approximately 0.375″ which are disposed onthe first sheet 66 in a nested array such that the center of spacers 64in adjacent rows/columns are offset with respect to one another. Theorifice 72 formed through spacer 64 is about 0.050″ (50 mils). Spacers64 are distributed on first sheet 66 at a density of about 6.25 spacersper square inch. As presently preferred, the pillars 68 in the secondarray are also circular disks having a diameter of approximately 0.125′which are disposed on the first sheet 66 such that a subset of fourpillars 68 are equiangularly superposed over at least a portion of thearea defined by the subjacent spacer 64. Pillars 68 are distributed onfirst sheet 66 in a density of about 25 pillars per square inch.

While the above-described configuration of spacers 64 and pillars 68 arepresently preferred, one skilled in the art will recognize that thesize, shape, density, distribution and location of the spacers andpillars within the fuel cell may be selected in accordance with thespecification and operational parameters of a given fuel cellapplication. For example, as illustrated in FIG. 5A, spacers 64′ areconfigured as nested hexagons with an orifice 72′ formed therethrough. Aset of pillars 68′ are configured as triangles with a subset of sixtriangles superposed over a portion of the area defined by the subjacentspacer 64′. In another example illustrated in FIG. 5B, spacers 64″ areconfigured as nested squares with an orifice 72″ formed therethrough. Aset of pillars 68″ are configured as squares with a subset of foursquares superposed over an area defined by multiple subjacent spacers64″. The terms superposed and subjacent are used in relative termsherein, and one skilled in the art should recognize that the order ofadjacent components within the fuel cell 10 may be inverted.

With reference again to FIGS. 2, 3A-3B and 4A-4D and FIG. 6A-6B, theseparator plate 60 will be described in greater detail. An inboard majorface 84 of the first sheet 66 and an inboard major face 88 of the secondsheet 76 define an inlet manifold 90 therebetween. Fluid communicationbetween the inlet manifold 90 and the inlet header 80 is established bya plurality of runners 92 formed in a frame 122. The frame 122 may beinterposed between the first sheet 66 and the second sheet 76. Forexample, the frame 122 may be laminated between the first sheet 66 andthe second sheet 76 and may circumscribe the pillars 68. The height ofthe inlet manifold 90 is defined by the height of the pillars 68. Anexhaust manifold 100 is defined between an outer face 104 of the firstsheet 66 and an adjacent face 108 of the diffusion medium 30. In thismanner, the inlet manifold 90 and the exhaust manifold 100 function as aplenum throughout which the pressure is substantially constant, i.e.,very little pressure differential within the manifold areas. Fluidcommunication from the exhaust manifold 100 to the outside of the stackis achieved by direct connection of this manifold to the atmosphere. Inother words, manifold 100 is open to atmosphere all along its perimeter.The height of the exhaust manifold 100 is defined by the height of thedisks 64. As presently preferred, the inlet header 80 is formed alongone margin of the separator plate 60. No exhaust header, other than thedirect connection of the manifold 100 to the atmosphere exists. However,one skilled in the art will recognize that the inlet header and exhaustheader may be configured in any suitable manner to provide fluidcommunication of the reactant gas into and out of the flow field.

Electrically conductive connectors 110 are disposed through vias 112formed through the first sheet 66, the pillars 68 and the second sheet76. The connectors 110 are aligned to electrically connect the pillars68 with the corresponding disks 64.

The connectors 110 provide electrical continuity from the diffusionmedium 30 to an outside face 116 of the second sheet 76, therebyallowing current to be carried across the entire thickness of theseparator plate 60 and consequently across the entire fuel cell stack10. The connectors 110 may comprise vias having conductive materialdisposed entirely therein or alternatively on an inner circumferentialwall thereof for example. The conductive material may comprise graphitefor example.

With continued reference to FIGS. 4B-4D and 6A-6B, the operation of theseparator plate 60 will be described. The flow path of the reactant gasis characterized in three distinct flow segments namely, a delivery leg(D), an active area leg (A) and an exhaust leg (F). During the deliveryleg (D), the reactant gas enters the separator plate 60 at the inletheader 80 and flows through the inlet manifold 90. The reactant gasflows relatively freely (i.e., with no significant pressure drop and nopredetermined path) around the respective pillars 68 and is containedwithin a lateral boundary (FIG. 3) in the inlet manifold 90 defined byan interior edge 120 of the frame 122. From the inlet manifold 90, thereactant gas is directed through the respective orifices 72 in the disks64 and the first sheet 66.

The active area leg (A) is designed to have a controlled pressure drop.Because the active area leg (A) accounts for nearly all the pressuredrop of the flow path, it includes a flow-interfering medium that has awell-controlled permeability, length and cross-sectional area. Theflow-interfering medium has lower permeability relative to empty spacein the inlet/exhaust manifolds 90, 100 in order to guarantee that thepressure drop of the active area leg (A) is significantly higher thanthe delivery leg (D) and exhaust leg (E). During the active area leg(A), the reactant gas enters the flow-interfering-medium 30 from theorifice 72 passes across the face of the MEA (not shown) and exits theflow-interfering medium 30 at an outer boundary 126 (FIG. 4A) of thespacer 64.

As shown in FIGS. 2 and 4D, the active area leg (A) is radial from theorifice 72 adjacent the surface of spacer 64. In this manner, a planaror 2-dimensional flow field, as compared with a channeled or1-dimensional flow field, is provided which enables a differential flowdistribution across the reactive face of the MEA. The dimension of thespacer 64 establishes the length of the flow path (A). The number ofspacers 64 establishes the number of parallel paths. Thus, the planarflow field is similar to an interdigitated channel flow field but ismuch less susceptible to water blockage since the reactant gas is notconstrained to flow in one dimension within the channel. Thisinterdigitated-like flow field is beneficial because oxygen is carriedthrough the primary current collectors by convection rather thandiffusion allowing for significantly lower mass transport losses.

The perimeter of spacer 64 multiplied by the diffusion medium thicknessestablishes the cross sectional area of the flow path (A). Thepermeability of the diffusion medium establishes the permeability of theflow path. Hence, these parameters establish the pressure gradient andoverall pressure drop of the active area leg (A) depending on the numberof parallel paths over the active area. The degree to which an even flowdistribution over each parallel path is achieved is determined bytolerances to which these parameters can be held. Because thedimensional variations (radius and thickness) are most likely smallcompared with the variation in diffusion medium permeability, thepermeability of the diffusion medium determines how evenly flow becomesdistributed. The flow field of the present invention is very effectiveat removing water since the pressure drop is concentrated over arelatively short active area leg. As a result, the gas velocity in thissegment of the flow path is very high so that liquid water will beforcefully moved away from the velocity of the MEA and into the exhaustmanifold where it can be expelled from the fuel cell.

Returning now to FIGS. 4B and 4D, the exhaust path (E) is defined fromthe point at which the reactant flow leaves the flow-interfering medium30 at the edge 126 of the spacer 64 to the point the flow exits theseparator plate 60 through the exhaust header 82. The exhaustive flownegotiates relatively freely (i.e., with no significant pressure drop orpredetermined path) around the outer boundaries 126 of the spacer 64 andis contained within a frame or seal 130 (FIG. 2).

Turning now to FIGS. 6A and 6B, two separator plates 60, as describedherein, are arranged in a back to back configuration and make up thebipolar plate 20. It is appreciated that the second sheet 76 asrepresented in FIG. 4A may comprise a single sheet when arranged in thebipolar plate 20. For clarity, a second separator plate is shown havinglike components and are referenced by numerals incremented by 200. Inthe configuration as shown, the separator plate 60 is arranged todeliver cathode reactant to the flow-interfering medium 30 and theseparator plate 260 is arranged to deliver anode reactant to theflow-interfering medium 28. The electrical connectors 110 align withcomplementary electrical connectors 210 to provide electricalcommunication between adjacent MEAs 14 and 16.

With reference now to FIG. 7, a method of making the separator plate 60is graphically present in a flow chart generally at reference 300.Construction of the flow field is accomplished using flex-circuitmaterials and fabrication techniques. In step 302, a first sheet ofconductive material is laminated onto a gas impermeable polymeric filmsuch as a polyimide film. The conductive material is preferablystainless steel having a thickness of 0.010″ (10 mils) for example. Thepolyimide film is preferably 0.002″ (2 mils) thick sheets of material. Asuitable polyimide film includes Kapton® manufactured by the E.I. DuPontCorporation. In step 304, the conductive material is etched into adesired pattern such as an array of disks. After etching, the array ofdisks preferably extend 0.010″ from the polyimide.

In step 306, the passages are formed in the disks. The passages may beformed by any suitable technique such as etching. In step 308, a secondsheet of conductive material is laminated onto a second sheet ofgas-impermeable polymeric film. As presently preferred, the second sheetof conductive material is 0.010″ (10 mils) stainless steel and thesecond sheet of polymeric film is 0.002″ (2 mils) Kapton® film. In step312, the conductive layer is etched to form the pillars in a similarmanner as described with respect to the disks. In step 318, the pillarside of the second sheet of polyimide film is laminated onto the firstsheet of polyimide film on a surface opposite the disks. The spacecreated between the first and second polyimide sheets defines thedelivery path or inlet manifold. In step 324 vias are incorporated intothe separator plate and extend through the second sheet of polyimide,through each of the pillars and through the first sheet of polyimide.

In step 330, electrically conductive material is disposed through thevias to form electrically conductive paths. The electrically conductivepaths may be formed by filling the vias entirely with conductivematerial or by coating the circumferential wall of the vias withconductive material. The electrically conductive paths allow current tobe carried across the entire flow field as well as between adjacentseparator plates and ultimately the fuel cell stack as a whole.

Those skilled in the art can now appreciate from the foregoingdescription that the broad teachings of the present invention can beimplemented in a variety of forms. For example, the number of spacers 64shown on the separator plate 60 establishes the number of parallel flowpaths and may be configured with fewer or greater disks. The geometricalconfiguration of the spacers 64 may alternatively comprise other shapessuch as rectangles, triangles or trapezoids for example. Moreover, thepillars 68 defining the height of the inlet manifold 90 may comprisealternate shapes as described above. In addition, while it is shown thatfour pillars 68 compliment the single spacer 64, other ratios maysimilarly be employed. Therefore, while this invention has beendescribed in connection with particular examples thereof, the true scopeof the invention should not be so limited since other modifications willbecome apparent to the skilled practitioner upon a study of thedrawings, the specification and the following claims.

1. A fuel cell comprising: a first planar manifold defined between afirst gas-impermeable element and an active element; a plurality ofspacers disposed within said first planar manifold, each of saidplurality of said spacers and said first gas-impermeable element havingan orifice formed therethrough; a second planar manifold defined betweensaid first gas-impermeable element and a second gas-impermeable elementin a subjacent relationship to said first planar manifold; wherein aflow path is established from said second planar manifold, through saidorifice, across said active element, and back into said first planarmanifold.
 2. The fuel cell of claim 1 further comprising an electricallyconductive path extending through the fuel cell to provide continuityfrom said active element, through said plurality of spacers and saidfirst gas-impermeable element to said second gas-impermeable element. 3.The fuel cell of claim 2 wherein said plurality of spacers areelectrically conductive so as to establish said electrically conductivepath.
 4. The fuel cell of claim 3 wherein said electrically conductivepath further comprises an electrically conductive filler disposed in avia formed through said first gas-impermeable element.
 5. The fuel cellof claim 1 wherein said first gas-impermeable element is disposed in asubstantially parallel spaced relation to said second gas-impermeableelement such that said first planar manifold is substantially parallelwith said second planar manifold.
 6. The fuel cell of claim 1 furthercomprising a second plurality of spacers disposed within said secondplanar manifold.
 7. The fuel cell of claim 1 wherein said plurality ofspacers comprise a nested array of spacers disposed on said firstgas-impermeable element.
 8. The fuel cell of claim 1 further comprisinga frame interposed between said first gas-impermeable element and saidsecond gas-impermeable element.
 9. The fuel cell of claim 1 wherein saidplurality of spacers are equidistantly spaced on said firstgas-impermeable element within said first planar manifold.
 10. The fuelcell of claim 1 wherein said active element comprises a flow-interferingmedium.
 11. The fuel cell of claim 6 further comprising an electricallyconductive path extending through the fuel cell to provide continuityfrom said active element through said plurality of spacers, said firstgas-impermeable element, said second plurality of spacers, and saidsecond gas-impermeable element.
 12. The fuel cell of claim 11 whereinsaid plurality of spacers and said second plurality of spacers areelectrically conductive.
 13. The fuel cell of claim 12 wherein saidelectrically conductive path further comprises an electricallyconductive filler disposed in a via formed through each of said firstand second gas-impermeable elements.
 14. The fuel cell of claim 6wherein a subset of said second plurality of spacers are at leastpartially superposed over an area defined by a subjacent spacer of saidplurality of spacers with said first gas-impermeable element interposedtherebetween.
 15. The fuel cell of claim 6 wherein a subset of saidsecond plurality of spacers are completely superposed over an areadefined by a subjacent spacer of said plurality of spacers with saidfirst gas-impermeable element interposed therebetween.
 16. The fuel cellof claim 6 wherein a subset of said second plurality of spacerscomprises a superposed spacer over an area defined in part by a pair ofsubjacent spacers of said plurality of spacers.
 17. The fuel cell ofclaim 6 further comprising a frame circumscribing said second pluralityof spacers.
 18. The fuel cell of claim 17 further comprising a headerformed in said frame and in fluid communication with one of said firstplanar manifold and said second planar manifold.
 19. The fuel cell ofclaim 18 further comprising a set of runners formed in said framebetween said header and one of said first planar manifold and saidsecond planar manifold.
 20. The fuel cell of claim 6 wherein each spacerof said plurality of spacers comprise a disk with said orifice formed ata center thereof.
 21. The fuel cell of claim 6 wherein each of saidfirst and second gas-impermeable elements comprise polyimide film. 22.The fuel cell of claim 6 wherein each spacer in said plurality ofspacers and said second plurality of spacers comprise stainless steelelements.
 23. The fuel cell of claim 6 wherein said second plurality ofspacers comprise a nested array of spacers.